In the manufacture of food and drink of various kinds, a variety of saccharides such as sucrose, corn starch syrup, glucose, maltose and high-fructose corn syrup have been used as sweeteners. However, these saccharides, which comprise glucose, fructose or a sugar formed of .alpha.-glucosidic linkage of glucose and are digested in living orgnaisms and accumulated as caloric sources, have the problem that an excessive intake thereof may cause corpulence or may bring about adult diseases such as diabetes.
A non-caloric synthetic sweetener such as Aspartame has been also developed. Since, however, synthetic sweeteners are not natural products, there is anxiety about the safety to human bodies.
In the recent trend of consumption of food and drink, people avoid sweetness more than ever, and tend not to be satisfied if food and drink is seasoned only with a sweetener.
On the other hand, in recent years, intestinal floras (the aggregate of bacteria) is known to concern the health of humans, and there is an increasing interest in the intestinal floras. For example, Bifidobacteria are one of main bacterial species that constitute human intestinal floras, and is known, for example, to inhibit growth of putrefactive bacteria or pathogenic bacteria, thus playing a variety of useful physiological roles in humans or animals. The Bifidobacteria may decrease or disappear because of various diseases or aging, and hence it has been variously attempted to increase Bifidobacteria in intestines.
As food or medicine suited for such a purpose is known to include, for example, yoghurt containing Bifidobacteria, powder of Bifidobacteria, and oligosaccharides capable of growing Bifidobacteria. Of these, the oligosaccharides capable of growing Bifidobacteria are of current interest. Reported as those having the effect of growing Bifidobacteria are fructooligosaccharide, soybean oligosaccharide, konjak oligosaccharide, isomaltooligosaccharide, galactooligosaccharide, and so forth. Part of these has been already made commercially available as health food materials.
Lactic acid bacteria (or Lactobacilli) are also known from old times as useful bacteria that affect intestinal floras. The lactic acid bacteria, like Bifidobacteria, are also considered to play roles to inhibit intestinal growth of putrefactive bacteria. Thus, viable lactic acid bacteria are mixed in an intestinal regulator, or drinks containing lactic acid bacteria are commercially available.
The effect of promoting the growth of Bifidobacteria, attributable to the oligosaccharides described above, is caused by the action of Bifidobacteria such that it can decompose the oligosaccharides to utilize them as nutrient sources although most other bacteria can not decompose the oligosaccharides, and consequently the Bifidobacteria selective grow. These oligosaccharides, however, are not necessarily selectively utilized only by Bifidobacteria, and there exist bacteria other than Bifidobacteria, that utilize the oligosaccharide for their growth. It depends on the kinds of oligosaccharides what sorts of bacteria can utilize the respective oligosaccharides and what sorts of bacteria can not utilize them. Under the existing circumstance, this can not be made clear unless experiments are actually tried.
The intestinal floras are comprised of a great number of bacteria living together in intestines. Even when the Bifidobacteria have become temporarily predominant in intestines, its influence may readily change. Thus, it is preferred to promote the growth of not only Bifidobacteria but also other useful bacteria such as lactic acid bacteria in order to stably obtain the effect of improving intestinal floras. In other words, the influence of lactic acid bacteria and so forth may also be increased together with that of Bifidobacteria, so that the effect of inhibiting the growth of putrefactive bacteria such as Welch bacilli (Clostridium perfringens) can be obtained in a stable state.
Researches hiterto made on the improvement in intestinal floras by the use of oligosaccharides have been mainly focused only on the action of promoting the growth of Bifidobacteria. Under existing circumstances, studies have not been made so much on the effect on other useful bacteria such as lactic acid bacteria.
With regard to the lactic acid bacteria, viable lactic acid bacteria have been used in intestinal regulators or drinks. These, however, are not used for the purpose of improving the growth environment of lactic acid bacteria in intestines. Hence, even if the influence of lactic acid bacteria is temporarily increased by ingestion of living bacteria, no stable effect of improving intestinal floras can be expected since their influence may readily change because of the presence of other bacteria having better adapted themselves to the environment.